Production of high purity titanium by metallic sodium reduction of titanic halide



1962 D. H- BAKER. JR., ET Al. 3,069,255

PRODUCTION OF HIGH PURITY TITANIUM BY METALLIC SODIUM REDUCTION OF TITANIC HALIDE Filed Nov. 25, 1957 Helium or Argon 2/ Hal/um Pressure 2/0 confra/s etc. I TIC/ 20 Va or 200 p 26 I6 32 faz INVENTOR. D. H. Baker, Jr. V. E. Homme rates 3,069,255 PRGDUCTION OF HIGH PURITY TITANIUM BY METALLIC SODBUM REDUCTION OF TRTANEC HALIDE Don H. halter, Jr., and Vernon E. Homme, Boulder City,

New, assignors to the United States of America as represented by the Secretary of the Interior Filed Nov. 25, 1957, Ser. No. 693,883 '7 Claims. (Cl. 75-345) (Granted under Title 35, US. Code (1952), sec. 266) The invention herein described and claimed may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of royalties thereon or therefor.

This invention concerns a process for the recovery of titanium metal in substantially pure crystalline form.

It has long been sought to produce titanium economically in a substantially pure homogenous form. De-

composition of titanium tetrachloride on a heated filament yields the pure metal directly, but the process is not suitable for production on more than a laboratory scale. The other methods in common use heretofore produce titanium contaminated in varying degrees by nitrogen, oxygen, etc. In order to obtain a purified metal, further refining steps must be employed. In the Kroll process, which is one of the most commonly employed methods for producing titanium, the metal produced is heterogenous. Before use for most purposes it must undergo an expensive purification treatment. In addition, the titanium recovered from the Kroll process is a solidifled mass, which must be bore-d'out on a lathe, or otherwise removed from the reaction crucible-a time consuming and expensive operation.

It is an object of the present invention to provide an improved method for the preparation of titanium having a relatively low Brinell hardness number, in relatively pure crystalline form.

Another object of the invention is to provide an proved method for producing titanium by the reduction of titanium tetrachloride using sodium.

A further object of the invention is to provide a method for producing titanium wherein titanium tetrachloride is first reduced with sodium to lower valent chlorides, and then these latter are further reduced with additional sodium to titanium metal.

A further object is to separate crystalline titanium metal, produced by the sodium reduction of titanium chlorides, from molten salt by a simple drainage method. Other objects will appear hereinafter in the specification and claims.

These objects are achieved by first partially reducing titanium tetrachloride to the diand trichlorides by dropping molten sodium through titanium tetrachloride vapors at a temperature of 400 to 750 C. This intermediate product is then converted to the desired form of crystalline titanium in a second stage treatment, as follows:

(1) To make a crystalline product that is predominantly composed of needle-type crystals, the reaction chamber is heated to 805 87 C. and additional sodium added slowly to convert the lower chlorides of titanium to metal and salt. After the reaction is complete the molten salt is permitted to drain off from the titanium needle and granular crystal product, which can then be readily removed from the reactor. The slow reaction of the sodium with the titanium diand trichlorides produces high purity titanium needles having a chlorine content as low as .01 percent and a Brinell hardness number as low as 60. Runs A to I in Table 1 illustrate this mode of operation.

(2) To make more dense crystals havina a granular or dendritic shape, the reaction chamber is cooled to freeze the first-stage melt. The required amount of sodium is then added en masse and the reaction chamber heated gradually to the melting point of the first-stage product. An initial reaction takes place in the upper portion of the melt, but soon subsides. To obtain further reduction, the reaction chamber is heated to 750 805 C. and maintained at this temperature until the reaction is complete. The molten salt is then permitted to drain from the reaction product and the crystals can then be readily removed from the reactor. A crystalline metal has been made having a Brinell hardness number as low as 49. Run J in Table 1 illustrates this mode of operation.

The FIGURE is a schematic sectional diagram of one form of apparatus which may be employed to carry out the invention.

In the drawing, 1 is a cylindrical chamber having an upper flange 2 and a lower sealing plate 13. Fastened to the upper flange by four 0 clamps 3 is an upper plate 4 having nipples 5 and 6 and gland 7 mounted therein. Gasket Zaacts as a seal between flange 2 and plate 4. Passing through gland 7 is a valve stem 8, having an upper handle 9, of a wire probe valve composed of seat number 10 threadably mounted in plate 13, and the stem 8. Compression cap 11 and packing 12 act to seal valve stem 8. An electrical heating coil 33 surrounds chamber 1.

Mounted below chamber 1 is a larger diameter cylindrical chamber 14 having upper and lower flanges 15 and 16. Chamber 14 is joined to chamber 1 by means of a plurality of clamps 17, of which only one is shown, which act to removably fasten plate 13 to flange 15. A gasket 18, of a suitable material, such as neoprene, is used as a seal. Water tubes 19 serve to cool the flanges and thereby prevent damage to the seal. Angularly mounted in plate 13 is nipple Zila, having threadably mounted thereon packing gland seal 20, having a compression cap member 21 fastened by bolts at its upper end. Passing through an opening in 21 and gasket 21a, and having a gas-tight sliding fit is pointed steel rod 22. Also angularly mounted in plate 13 is nipple 34a, having threadably mounted thereon packing gland seal 34, having a compression cap 35 fastened by bolts at its upper end. A pipe thermocouple well 36, sealed on the lower end passes through an opening in 35 and on through the packing 35awhich provides a gas-tight sliding fit. A thermocouple 37 is inserted in well 36. Lower chamber 23 is of the same diameter as 14 and has upper and lower flanges 24 and 25. Sheet metal diaphragm 26, which is welded to flanges 16 and 24, separates chambers 14 and 23 in the manner shown, and plate 27 welded to flange 25 is the bottom closing member. Tubes 28, 29 and 30 permit access of reagents, purge gases, etc, into chambers 14 and 23. As shown, 29 and 31 are in communication with each other and act to equalize the pressures in 23 and 14. 31 and 32 are the beads resulting from the welding operation.

The lower portion of the apparatus, consisting of chambers .14 and 23, is mounted vertically in an electric furnace (not shown), such as one heated by silicon carbide resistance rods. By varying the power input to the fur nace, the temperature of the reactor may be controlled.

In operation, sodium is introduced in chamber 1 and heated to melting under an atmosphere of argon, helium, or other inert gas introduced through nipple 5. Chambers 14- and723 are evacuated through lines 29 and 30 and backfilled with an inert gas, preferably helium. Hot (20()450 C.) titanium tetrachloride vapors are then introduced into the chamber 14. The valve stem 8 is then opened to permit molten sodium to fall dropwise through the titanium chloride vapors, the temperature of the chamber being maintained at 400750 C.

Here a sufficient amount of sodium reacts with titanium tetrachloride to form a complex or molten mixture 7 of salt (NaCl) and lower valent titanium chlorides, which is supported on diaphragm 26. This phase of the process depends on many variables including the size of the sodium feed orifice, length of drop through the hot zone, rate of titanium tetrachloride feed, and the temperature of the feed. During this firstrstage reduction some titanium metal is formed along with the lower chlorides of titanium. Maintaining the stoichiometric balance for the reaction, 2Na+TiCl TiCl -l- 2NaCl then causes an excess of TiCl in the melt. The melt is soaked at a temperature above its melting point to convert this T1013 to TiCl according to the reaction 2TiCl +Ti- 3TiCl 7 reduction, the reactionchamber is maintained at the reduction temperature for a period of time sufficient for the reaction to be completed, which varies with the depth of the melt. At the end of this period, pointed steel. rod

22 is forced down and punctures diaphragm 26. The

molten salts then drain into the lower chamber 23 leaving the titanium needles and/or crystals on the diaphragm.

4 After cooling, the welding beads 31 and 32 are then ground off and the products removed.

After removal oftne metal product from the reactor, the residual sodium chloride and unreacted lower chlorides of titanium (if present) are leached from the titanium with a cold dilute acid, such as HCl, H etc. The pH of the leach solution is maintained below 2.0 to prevent hydrolysis of any titanium in the solution. After draining oil? the leach solution, the metal is washed in cold water and then dried. Fine metal, caused by a vapor reaction during reduction, contains most or" the impurities and is removed by screening through an -mesh screen. If sized, pure crystalline metal products 7 are desired, further screening can be used and a hydraulic classification made on each sized product to remove the granular agglomerations of fine metal associated with the crystalline metal. While we have shown and described a form of ap paratus which we have found suitable for carrying out the rocess, it is obvious that this equipment may be modified in a number of ways as desired. ForeXample, instead of providing means for puncturing the diaphragm for salt drainage, valves, tap holes, or a siphon can be utilized, heating means other than the coils shown may be employed, etc. Aside from modificationns in the apparatus shown, other entirely different forms may be devised to conduct this step reaction under a blanket of inert gas. As an example, two separate heated reaction vessels could be employed for each of the reaction stages.

7 EXAMPLE Various runs were made in the apparatus shown in the FIGURE. The following tables summarize the results obtained: a

Table 1 I RUN DATA FROM SEVERAL TWO-STAGE REDUCTIONS Feed Materials Feed Temperatures Furnace Tcmpera- Time of Reductures, OJ tion, Hours Run N0.

Sodium TiCl Sodium TiCh,

abs) abs.) 0 Q 0 C. 1st Sta e 2d Stage S1320 ZdStage 1 Time of feeding. I Use of technique for making dense granular and dendritic crystals.

Table 2 TWO-STAGE REDUCTION, METAL RECOVERY, AND METAL HARDNESS DATA Soaking Metal Data Y Fraction 7 Run N0. First-Stage Second-Stage Crystalline Average 1 100 Ti Metal Titanium BHN BHN Recovery (percent) (percent) Hours Temp., Hours Temp., Pounds BHN 1 The average Brinell hardness number was calculated from BH-N values of all size fractions, not from an actual composite.

R The long periods of first-stage soaking are not necessary but were more convenient for single shift operation. Three to six hours is adequate for the melt depths'and equipment used. This is also true of the second- 7 stage soaking, except when using the technique employed for Run No. I.

The soaking periods for both steps do not include the time of reduction shown in Table 1.

Table 3 CHEMICAL ANALYSES OF TITANIUM METAL PRODUCTS Chemical Analyses, Percent Reduction Product Mesh Size BHN Number H3 N: F e Na S 012 C Si E Needles 4-|l4 68 0.011 0. 034 0. 002 0.008 g3 012 045 002 010 0 68 004 017 001 007 224 .271 180 003 O1 003 004 002 007 152 025 050 002 006 Coarse crystals +4 49 O03 008 (102 005 do -28+14 57 003 012 001 005 I d0 14+38 62 .002 .015 001 02 It will be understood that various modifications and variations may be effected without departing from the spirit of this invention.

We claim:

1. The method of preparing titanium metal which comprises the steps of (1) reacting at an elevated temperature in a reaction zone completely blanketed with an inert gas, TiCl in the vapor state initially received over the entirety of said reaction zone, with a quantity of molten sodium in an amount sufficient to reduce the TiCl; to lower chlorides, whereby a molten mixture comprising lower valent titanium chlorides, including TiCl so dium chloride and some titanium metal is produced; (2) continuing the reaction for a time suflicient to react completely all the sodium present and to react all the titanium metal formed with TiCl to produce TiCl (3) increasing the temperature in the reaction zone; (4) adding molten sodium to the molten mixture in an amount at least suflicient to reduce the titanium chlorides to titanium; (5) continuing the reaction for a time sufficient to react the sodium present, whereby crystalline titanium is formed; and (6) draining off the molten material and recovering high purity crystalline titanium as a product of the process.

2. The method of preparing titanium metal which comprises the steps of introducing heated TiCl vapor into the entirety of a hot reaction zone completely filled with inert gas, passing molten sodium downwardly through said zone receiving said heated TiCl vapor in an amount sulficient to reduce the titanium tetrachloride to lower chlorides, whereby a molten mass of unreacted sodium, salt and lower valent titanium chlorides, including TiCl is formed, together with some titanium metal and accumulates at the bottom of said reaction zone, continuing the reaction for a time sufiicient to react completely the sodium present and to react the titanium metal formed with TiCl to form TiCl increasing the temperature in the reaction zone, adding additional molten sodium to the liquid mass at an increased rate in an amount at least suiiicient to reduce the lower valent titanium chlorides to titanium, continuing the reaction until substantially all the titanium chlorides are completely reduced, draining ed the molten material, and recovering high purity crystalline titanium as a product of the process.

3. The method of preparing titanium metal which comprises the steps of introducing titanium tetrachloride vapors at a temperature at about 200 to about 450 C. into the entirety of a reaction zone completely filled with inert gas, passing molten sodium, at a temperature not in excess of about 175 C., downwardly through said zone receiving said titanium tetrachloride vapors, maintaining the temperature of said zone at a temperature of from about 400 to about 750 C., said sodium being added in an amount suflicient to reduce the titanium tetrachloride to lower chlorides, whereby a molten mass of unreacted sodium, salt and lower valent titanium chlorides, including TiCl is formed together with some titanium metal and accumulates at the bottom of said reaction zone, continuing the reaction for a time suflicient to react completely the sodium present and to cause all of the titanium forced to react with TiCl to form TiCl increasing the temperature of the reaction zone to within the range of about 805 C. to about 875 C., adding additional molten sodium to the liquid mass at an increased rate in an amount at least sufiicient to reduce the lower valent titanium chlorides to titanium, continuing the reaction until substantially all the titanium chlorides are completely reduced, draining oil the molten material, and recovering high purity crystalline titanium as a product of the process.

4. The method of claim 3, including, subsequently to draining oif the molten material, the steps of leaching the remaining crystalline titanium mass with a dilute acid having a pH below about 2.0, draining off the leach solution, washing with cold water, drying, and then screening to remove any fines.

5. The method of preparing titanium metal which comprises the steps or" introducing titanium tetrachloride vapors at a temperature of about 200 C. to about 450 C. into the entirety of a reaction zone completely filled with inert gas, passing molten sodium, at a temperature not in excess of about C., downwardly through said zone, maintaining the temperature of said zone from about 400 C. to about 750 C., the sodium being added in an amount sufficient to reduce the titanium tetrachloride to lower chlorides, whereby a molten mass of unreacted sodium, salt and lower valent titanium chlorides, including TiCl is formed together with some titanium metal and accumulates at the bottom of said reaction zone, continuing the reaction for a time sufiicient to react completely the sodium present, and to cause all of the titanium present to react with TiCl to form TiCl cooling the reaction zone to freeze the melt, adding additional molten sodium en masse in an amount at least sufiicient to reduce the lower valent titanium chlorides to titanium, increasing the temperature of the reaction zone to the melting point of the melt, whereby an initial reduction reaction occurs in the upper portion of the melt, then heating the reaction Zone to a range of from about 750" to about 805 C., continuing the reaction until substantially all the titanium chlorides are completely reduced, draining off the molten material, and recovering crystalline titanium as a product of the process.

6. The method of claim 5, including, subsequently to draining off the molten material, the steps of leaching the remaining crystalline titanium mass with a dilute acid having a pH below about 2.0, draining oi the leach solution, washing with cold water, drying, and then screening to remove any fines.

7. The method of preparing titanium metal which comprises the steps of (1) reacting, at an elevated temperature in a reaction zone completely blanketed with inert gas, TiCl in the vapor state initially received over the entirety of said reaction zone, with a quantity of molten sodium in an amount sufiicient to reduce the TiCl to lower chlorides, whereby a molten mixture comprising lower valent titanium chlorides, including TiCl sodium chloride and some titanium metal is produced; (2) continuing the reaction'for a time sufiicient to react completely all the sodium present, and to react all the tita- (5) heating the reaction zones to from about 750 C. to about 805 C., until substantially-allthe titanium chlorides are completely reduced; (6) draining off the molten material and recovering high purity crystalline titanium as a product'of the process.

References Cited in the file of this patent UNITED STATES: PATENTS 2,826,493 Garrett et al. Mar. 11, 1958 Quinn a Dec. 10, 1957 8, 2,828,199 Findlay Mar. 25, 1958 2,846,304 Keller et al Aug. 5, 1958 2,847,297 Dipietro Aug. 12, 1958 2,847,298 Vaughan Aug. 12, 1958 2,848,319 Keller et al Aug. 19, 1958 2,856,335 Rick Oct. 14, 1958 2,890,953 Hill et a1 June 16, 1959 2,895,823 Lynskey July 21, 19 59 7 2,936,232 Vaughan May 10, 1960 FOREIGN PATENTS 7 Great Britain June 13, 1956 OTHER REFERENCES 'Maddex et aL: Journal of Metals, April 1950, pp. 

1. THE METHOD OF PREPARING TITANIUM METAL WHICH COMPRISES THE STEPS OF (1) REACTING AT AN ELEVATED TEMPERATURE IN A REACTION ZONE COMPLETELY BLANKETED WITH AN INERT GAS, TICI4 IN THE VAPOR STATE INITIALLY RECEIVED OVER THE ENTIRETY OF SAID REACTION ZONE, WITH A QUANTITY OF MOLTEN SODIUM IN AN AMOUNT SUFFICIENT TO REDUCE THE TICI4 TO LOWER CHLORIDES, WHEREBY A MOLTEN MIXTURE COMPRISING LOWER VALENT TITANIUM CHLORIDES, INCLUDING TICI3, SODIUM CHLORIDE AND SOME TITANIUM METAL IS PRODUCED; (2) CONTINUING THE REACTION FOR A TIME SUFFICIENT TO REACT COMPLETELY ALL THE SODIUM PRESENT AND TO REACT ALL THE TITANIUM METAL FORMED WITH TICI3 TO PRODUCE TICI2; (3) INCREASING THE TEMPERATURE IN THE REACTION ZONE; (4) ADDING MOLTEN SODIUM TO THE MOLTEN MIXTURE IN AN AMOUNT AT LEAST SUFFICIENT TO REDUCE THE TITANIUM CHLORIDES TO TITANIUM; (5) CONTINUING THE REACTION FOR A TIME SUFFICIENT TO REACT THE SODIUM PRESENT, WHEREBY CRYSTALLINE TITANIUM IS FORMED; AND (6) DRAINING OFF THE MOLTEN MATERIAL AND RECOVERING HIGH PURITY CRYSTALLINE TITANIUM AS A PRODUCT OF THE PROCESS. 